Process for lowering the pour points of mineral oils



Patented June 18, 1940 PATENT orrica PROCESS FOR LO POINTS GT'HEPOURwaam or MINERAL onls Franz Rudolf Moser,

Amsterdam, Netherlands,

assignor to Shell Development Company, San Francisco, Call! acorporation of Delaware No Application September 25, 1933,

Serial No. 690.949. tember 2'1, 1932 In the Netherlands Sep- 16 Claims.(or. 196-151 The invention relates to a process for reducinfl the pourpoints of mineral oils or mixtures containing mineral oils, or for themanufacture of such oils having relatively low pour points.

Some hydrocarbon oils, as for instance those originating from paraffinbase materials and those obtained by hydrogenation, may show a largeincrease of viscosity when the temperature is lowered. The viscosity mayeven be increased 10 to the extent of rendering the oil entirelyunpourable; This so-called "congelatlon" of the lubricating oil is to beascribed to the crystallizable or otherwise precipitable parafiln waxpresent therein. At a low temperature this paramn :5 wax forms aneedle-like structure in the oil, with the result that the latter losesits fluidity. It is'evident that lubricants having this property cannotbe used in engines operating at low temperatures.

Various methods have already'been proposed to separate the precipitableparaffin wax from the oil. It is known to freeze the oil, sometimes,after the addition of solvents, and subsequently to filter 0d thesolidified paraflin wax by means 25 of filter-presses or centrifuges. Itis further known to prevent the crystallization of parafiin wax at lowtemperatures by the addition of small or large quantities of specialsubstances, known as pour point reducers.

It was found that various hydrocarbons or hydrocarbon mixtures whichhave been subjected to polymerization or condensation treatment have theefiect of lowering the pour point of oils containing Wm components.Examples of such hydrocarbon mixtures are, for instance, the residuesobtained by cracking hydrocarbon oils or the products obtained bypolymerizing Edeleanu extracts, either by heating alone or by heating inthe presence of catalysts. It has been found N that, in order to obtainhydrocarbon mixtures with such pour point-reducing properties, theheatirn must be carried out at atleast a temperature where a cracking ofthe hydrocarbons at about tilt" 0.; cracked 4L5 residues are obtainedunder conditions complying with this requirement. Now it has beendiscovered that in these pour point-reducing hydrocarbon mixtures, whichmay be further referred to as pyrogenic condensation products,the 50active pour point-reducing substances can be concentrated in certainparts or fractions, which must be considered to be the of the pourpoint-reducing properties. These fractions, which can be separated invarious ways s-irom the inactive pyrogenic condensation prodbegins tooccur, e. g.

principal carriers ucts, may be best characterized by being insoluble inlight hydrocarbon mixtures having a low aro-. matic content. I

The process according to the invention consists in adding to ahydrocarbon oil, containing 5 waxy components, a product which isobtained by separating from a hydrocarbon mixture, which alreadycontains pour point-reducing substances, a fraction rich in suchsubstances which are substantially insoluble in having a low aromaticcontent. As is evident from its definition, this fraction may beseparated by precipitating it with a low-boiling naphtha or gasoline,poor in aromatics, or, by means of such other precipitants, as butane,15 pentane, alcohol-ether mixtures and in general those organic liquidswhich are or may be used to separate from asphalt and similar residualor tar-like materials the substances known in pc- 7 troleum technologyas asphaltenes, with which, 20

however, the pour point-reducing substances need not by any means beidentical. For instance various pour point-reducing substances accordlneto the invention are insoluble in benzol, whereas. as,it is known,asphaltenes are soluble therein to $5 some extent.

In the claims the precip'tants to be used according to the invention arereferred to as aliphatic solvents, which expression includes all thosesolvents which are or may be used to M separate asphaltenes from asphaltand similar residual or tar-like materials.

The separation of the active substances from mixtures containing themmay be efiected by fractionation, combined, if desired, with preoipiwtation by above described means. Various fractions obtainedby suchcombination treatment usually have diderent pour point-reducingactivities; some fractions are far moreactive than others; they also maydiffer in their colours, some, (w being black and others lighter. Inmany cases the latter will be chosen when it is a question of loweringthe pour point of lubricating oil since in that case the colour is notadversely enacted.

The pour point-reducing activity of substances precipitated by variousdiluents usually depends upon the precipitant (diluent) used; forinstance, with kerosene, as diluent, less material is usuallyprecipitated than with a light naphtha, but sometimes the precipitateappears to be more active. so

Further it has been found that the activity or the pyrogeniccondensation products can be increasedby heating. This second heatingmay be carried out under practically non-cracking conditions, e. y. at350? 0., in contrast to the on hydrocarbon mixtures 10 first heatingwhereby the pyrogenic condensation products are formed. This heating maytake place in a closed vessel. Also, the pyrogenic condensation productsmay be subjected to a distillaother known aids to distillation. Thisdistillation results in the concentrating of the active components inthe distillation residue (so that later less precipitant is required)and may also cause an increase in the activity of the pyrogeniccondensation products, as a result or heating during the distillation.It is evident, that the heating treatment at or about 350 C. and thedistillation, as described above, may be combined.

It has been found, that by properly regulating thetime and temperaturesof cracking, either followed or not by heating the pyrogenouscondensation products at non-cracking temperatures, thepour pointreducing substances of maximum activity can be produced. As a generalrule, commercial cracked residues, which are obtained under theconditions selected for a maximum production of gasoline, are notsufliciently cracked to yieldthe most active pour point reducers; it isadvantageous to subject such residues to. further polymerizing heattreatments, preferably without further cracking at temperatures about350 C. The active substances formed during such treatments reach acertain maximum (either quantitative or qualitative in character) andthen, if overheated, begin to decline in their ei' fectiveness. Byactually testing the materials obtained at various stages of thepolymerizing treatment, the optimum conditions for production of themost active product can be readily ascertained for any cracked residue.Sometimes it is found suitable to add the pyrogenic condensationproducts, activated by heating and/or concentrated by distillation,directly, without previous precipitation of the active substances, tothe hydrocarbon oil whose pour point is to be lowered.

The pour point-reducing substances may be added to the hydrocarbon oilseither in the form in which theyare obtained'or after being dissolved ina solvent; as suitable solvents, hydrocarbon mixtures of' aromaticcharacter, such as Edeleanu extract or tar oil, may be used for mak-'ing relatively concentrated solutions. If solutions of moderateconcentration are desired, then, for instance, lubricating oils may beused as solvents.

In order to promote the pointreducing substances in dissolving of pourhydrocarbon oils, a

moderate heating, say at a temperature of about 100 C., may be used.

The invention is applicable to various types oi. hydrocarbon oils; forinstance, the product man- 7 ufactured according to the invention mayeven be added to crude oils, in order to" prevent a deposit of well waxin the well, or used in the pipelines carrying crude -oils, etc.

It has been found that isolation of active pour point reducers could beparticularly readily attained by means of such light solvents as lowermembers of paraflinic series, like butane, pentane and hexane.

Examples I. Edeleanu extract from a Venezuelan lubriating oil fractionwas heated at 400 C. under pressure for 4 hours. The product obtainedwas f evaporated with steam until a volume equalto one-firth of thevolume of the original Edeleanu extract was obtained. This latter wastreated with an excess of naphtha with boiling range 60-80 C. Theseparated insoluble fraction was 'found to be 20 times as active, asregards pour point-reducing eilect, than the substances distion eitherwith or without steam, vacuum and solved in the naphtha, which werefound to constitute about 50% of the concentrate. 0.05% of thesubstances insoluble in the naphtha, calculated on the weight of aPennsylvanian turbine oil, was added with moderate heating to the oil,which had a pour point of 0.; as a result, the pour point of the turbineoil was reduced to 12 C. II. A residue obtained in the Dubbs cracking ofVenezuelan crude oil, when added in a quantity of 1% to a. Pennsylvanianlubricating oil with the original pour point of 0 C. reduced the-pourpoint of the oil by 18 C. A quantity of 0. 1% did not appreciably aiiectthe pour point.

The fraction precipitated from this cracked residue with 100 times itsvolume of pentane, which fraction constituted 26.7% ofthe residue,caused, when added with moderate heating in a quantity of 0.1% to thesame Pennsylvanian lubricating oil, a pour point reduction of 15 C.

The fraction soluble in pentane, when added in a quantity of 2% afterevaporation of the pentane, had no eflect on the pour point of thePennsylvanian oil. 5

III. Edeleanu extract from a heavy engine oil fraction of Venezuelanorigin was heated for 4 hours to 400 C. under a pressure of about 7atm.,

when a residue was obtained which constituted precipitate was'added tothe above-mentioned Pennsylvanian lubricating oil with moderate heating,whereby the pour point or the'oil was reduced to -12 C.

2% of the fraction soluble in pentaneadded after evaporation of thepentane had no eifect.

The foregoing examples demonstrate some of the methods of isolatingactive substances from pyrogenous condensation products and the'eifectsof such separated substances upon the pour points of oils containingwaxy components and having, therefore, relatively high pour points.

While certain specific liquids were particularly mentioned in the abovedescription as being suitable for treating residual products ofcracking, it

should be clearly understood that other liquid solvents for the inertportions of such residual products may be successfully used inseparating active pour point reducers from pyrogenous condensationproducts. Such solvents, which may include various straight runnaphthas, preferably boiling below 225 C., or light kerosenes, oralcohols, ethers, mixtures etc., may generally be characterized as beingof aliphatic nature, 1. e.

not aromatic; it should be realized, of course,

that small quantities of aromatic substances,

which may occur in commercial aliphatic solvents in quantities 'notexceeding 15% by vol-- me, are to be considered as permissible for thepurpose of this invention. When separating the active substances fromthe pyro enous condensation products-it was found very expedient in manycases to employ a series of precipitations oithe active substances fromsuccessively obtained precipitates. In other words, the inert substanceswere removed from the original mixture by a series of successiveextracting steps with portions of the same solvent or with differentsolvents belng'psed in each step.

Often it was found advantageous to iilte'r the mixture of pyrogenouscondensation products, particularly those, which contain granularcarbonaceous materials, and then proceed with the concentration of theactive pour point-reducing substances in the filtrate.

As a further feature 01. this invention, the

separation of active-pour point-reducing substances may be accomplishedby a method, which permits concentration or such substances separatelyfrom a gritty or granular material often found in cracked residues. Thismethod consists of precipitating such gritty material by diluting acracked'residue with a relatively heavy or high boiling diluent, such asdistlllates boiling above 225C. and preferably about 300 C. or higher,like stove oil-or gas oil, etc. Edeleanu extracts and other oils withsimilarly high contents of aromatics (15% or above) were found verysuitable for separating said gritty material from residues without anextensive loss oi active substances. Some of the active pour pointreducing substances are usually carried down with the precipitate butthe major portion of these substances remains in the diluted oil, or theilltrate, and is then recovered therefrom by precipitation with a lightaliphatic precipitant, such as described hereinbefore; the first diluent(high boiling) may be partly or completely distilled out of thefiltrate, or liquid portion of the diluted cracked residue, before thelow boiling diluent is added thereto.

As an example, a cracked Dubbs residue from cracking a topped crude wasdiluted with two volumes of a high boiling (rec-290 C.) kerosenedistillate (about 20% aromatics) at a temperature below 65 0.; and aprecipitate containing gritty particles was filtered oil. The filtratewas then mixed with about five volumes oi a pentane fraction of naturalgasoline (boiling range 28-38 C.) with the result that a new precipitateseparated out, which had a marked power of lowering the pour points ofparafin base oils; by adding as little as .2-.5% by weight of thisprecipitate to an oil having pour point -'7 C., this was lowered to --25C.

The first precipitate, which contained said gritty material was alsoextracted with a light naphtha at about 20 C., and the resultingundissolvecl material was found to be active as a pour point reducer,lowering the pour point of some of the Pennsylvanian lubricating oils byabout 8 0. when added in quantities oi about by weight.

As a modification of the described methods oi concentrating active pourpoint reducing substances, the following process has proved to be quiteuseful:

A sample oi the Udbhs residue was diluted with an untreated kerosenedistillate, and a pnecipitate containing a gritty car-mnaceous materialwas separated out from a liquid portion of the diluted cracked residue.A quantity oi commercial parafin was (about 20% by weight) was dissolvedthen in this liquid portion oi the cracked residue while heating it upto about 65 0. Upon cooling to about an E. a part oi the dissolved waxseparated out of the solution together with some dart-colouredcomponents of the red- Bill was filtered of! and then thoroughly washedwith the pentane fraction (B. P. 28-38 C.) to remove waxy components.

The remaining dark-coloured substances were found to possessconsiderable p'our point-reducing power, e. g. when .5% by weight wasadded to a paraiiin base lubricating oil, its pour point was loweredfrom '7 C. to -20 C.

The solution of the remaining wax in the diluted cracked residue wasalso found to contain the desired active substances. This solution wasdiluted with about five volumes of the pentane traction at an ordinaryroom temperature of about 20 0.; this caused a precipitate to separateout, which, when it was added in quantity of .5% by weight to theparaflin base oil, caused lowering of its pour point from -7C. to --20C.

It was generally observed, that the addition .of pour point-reducingsubstances to lubricating oils results in modifying their colours andcauses the oils to acquire the desirable green outertone. If necessary acareful acid treatment of the oils to which the pour point reducingsubstances are added may take place. Too intensive an acid treatment ortreatment with decolourizing powders cannot be recommended, as suchtreatment tends to neutralize partly or even wholly the pour pointreduction.

While various quantities of pour point-reducing substances of thisinvention may be used, these never need to exceed 1% by weight of theoil being treated.

I claim as my invention:

1. The method oi lowering the pour point of a -viscous mineral oilcontaining waxy components, which comprises incorporating into said oilthe active substances separated from pyrogenous condensation productsfrom mineral oil by precip-- itation with an aliphatic solvent.

2. In a process of lowering the pour point of a mineral oil containingwaxy components the steps of: diluting a mixture of pyrogenouscondensation products from mineral, oil with. a relatively low boilingaliphatic solvent, thereby causing precipitation of pourpoint-reducingsubstances from the mixture, separating the formed precipitate from thediluted mixture, and incorporating a small quantity of the separatedprecipitate into the said oil.

3. In a process of concentrating active pour point-reducing substancesfrom a mixture of pyrogenous-condensatlon products from mineral oil thesteps of: heating said mixture at elevated temperatures not exceeding400 C., separating a portion of the mixture which may vaporm at thesetemperatures from the less volatile portion, and diluting the latterwith a relatively low boiling aliphatic solvent thereby causingprecipitation of pour point-reducing substances.

d. In a process of concentrating active pour point-reducing substancesfrom a mixture of pvrogenous condensation products from mineral oil thesteps oi: diluting the mixture with an. aliphatic solvent, heating thediluted mixture to an elevated temperature, thereby substantiallydissolving the inert portion of the original mixture in the solvent;separating the undissolved portion from the mixture, and extracting saidportion with an aliphatic solvent at a room temperature, therebyconcentrating the desired active substances in a residue which issubstantially insoluble in said solvents.

5. An improved lubricating oil comprising a blend of aviscoushydrocarbon oil containing r due; this precipitate the rest of thecracked oil, diluting said products with a relatively low boilingaliphatic solvent, to separate soluble products from insolublecomponents, separating the insoluble components from the diluent, andthen adding the separated insoluble components to the oil containingwaxy components in proportion to cause a lowering of its pour point.

7. The method according to claim 6 in which the mineral oil is a liquidSoc-soluble portion of a mineral oil and the temperature is about 400 C.

8. The method of treating a hydrocarbon oil containing'waxy componentsto reduce its pour point which comprises reducing a cracked mineral oilresidue containing pyrogenous condensation products by distilling attemperatures which are below cracking temperatures, and adding theportion of the' residue which has been precipitated therefrom by a lowboiling aliphaticsolvent to said oil containing waxy components in-proportion to cause a lowering of its pour point.

9, The method 'of treating a hydrocarbon oil containing waxy componentsto reduce its pour point which comprises digesting a cracked mineral oilresidue containing pyrogenous condensation products at an elevatedtemperature which is below its cracking temperature, and adding theportion of the digested products which has been precipitated therefromby a low boiling ali-' phatic solvent to said oil containing waxycomponents in proportion to cause a lowering of its' pour point. n

10. The method according to claim 9 in which the digesting is conductedat a temperature 01' about 350 C.

11. The method of treating a hydrocarbon oil containing waxy componentsto' reduce its pour point which comprises'diluting a cracked mineral oilresidue containing pyrogenou's condensation products with a liquidhydrocarbon having a high aromatic content, filtering the mixture,mixing the filtrate with a relatively low boiling aliphatic solvent,separating the insoluble constituents from the diluent and then addingthem to said oil containing waxy camponents in proportion to cause alowering or its war point.

, 12. The method of treating a hydrocarbon oil containing waxy componmtsto reduce its pour point which comprises diluting a cracked mineral oilresidue containing pyrogenous condensation products with a liquidhydrocarbon having a high aromatic content, heating the resultingmixture and dissolving paraflin wax therein beyond the amount which issoluble at ordinary temperatures, chilling the mixture to precipitatewax and active pour point reducers, separating the precipitated productsfrom the liquid mixture, adding a relatively low boiling aliphaticsolvent to said precipitated products to dissolve the wax, separatingthe insoluble residue from the wax solution, and adding the insolubleresidue to said oil containing waxy components in proportion to cause alowering of its pour point.

13. A process for the production-of pour point depression agents frompetroleum pitch which comprises commingling said pitch with naphtha,separating the naphtha and dissolved fractions In from the insolubleresidue, commingling the insoluble residue with a lubricating oilfraction and separating the lubricating oil solution of pour pointdepression agents from the remaining insoluble residue.

14. A process for the production of pour point depression agents frompetroleum residue which comprises extracting said residue with naphtha,so as to obtain an insoluble portion, and admixing the insoluble portionto' a lubricating oil to dissolve active pour point depression agentsfrom said insoluble portion.

15. A process for the production of pour point depression agents from apitch produced from cracked petroleum which comprises comminglingsaid'pitch with naphtha, separating the naphtha and dissolved fractionsfrom the insoluble residue, cqmming ng the insoluble residue with alubricating oil fraction and separating the lubricating oilsolution ofpour point depression agents from the remaining insoluble residue.

116. A process for the production of pour point,

depression agents froma residue produced from cracked petroleum whichcomprises extracting said residue with naphtha, sons to obtain aninsoluble portion? andfidmixing the insoluble portion to a lubricatingoil to dissolve active pour point depression agents from said insolublepor I tion.

FRANZ RUDOLF MOSER.

